try

announcement.gemspec

@@ -36,11 +36,12 @@ if old_gemfile_text != new_gemfile_text
   a = Thread.new do
     Bundler.with_clean_env do
       puts 'waiting'
-      sleep
+      Thread.stop
       system("bundle update")
       puts 'test123'
     end
   end
+  sleep 0.1 while c.status!='sleep'
   a.wakeup
   a.join
   Thread.exit